Thanks for stopping by. This is where I publish a lot of my features and thoughts on HF propagation, antennas and other ham radio topics. I write for a number of radio magazines, including the RSGB's RadCom and ARRL's QST. I am also chairman of the RSGB's Propagation Studies Committee and produce the weekly HF propagation report for GB2RS. When not playing radio I'm a professional journalist specialising in aerospace, science and technology and am also author of four RSGB books.

Friday, 23 October 2009

What's this? G stations working VK on 10m at sunspot minimum? Jordan and Thailand audible on 10m on a 65ft end fed?

That can't be right!

Well, it looks like it is. So why did 10m suddenly open up this week?

I think we need to look at a number of factors. First the solar flux was 72 so obviously no massive increase in solar UV output has caused it.

But it is October and this is a peak month for DX. The ionosphere in the Northern Hemisphere is cooling down, becoming more dense and the chemical composition changes too in the Winter compared with Summer, giving us a greater ion density.

To quote J K Hargreaves' “The Solar Terrestrial Environment”: You get an increase in NO concentration and a decrease ion loss rate due to the removal of water-cluster ions and a change in chemical reaction rates due to the temperature change.

In fact, if you feeling really awake read the whole 414 pages – I am sure the more I read the less I understand!

Anyway, so is that the whole story? No!

At the time of the openings the he Bz (Interplanetary Magnetic Field) was pointing south which means that solar wind was coupling with the earth's magnetic field and hot ions were pouring in.

Hence the 6m aurora the previous night – see www.solarcycle24.com.

The three-hourly K index reached 4 showing the effects of these ions on the earth's magnetic field.

So what we probably saw was a pre-auroral enhancement and that condx on the upper HF bands while good, are going to get worse. I'll let you know if I was right.

And they say that a high K index is bad for propagation – not always at the outset though.

I bought one of these at a local rally. It is a 65ft wire and a 9:1 UN-UN. The guy who sells them is very friendly and is an ex Royal Signals op (I think). At only £30 it is barely worth making your own. I set it up as an inverted L with a 10m fishing pole. So it was about 9m up and about 10m sloping down to my shed, tied off with fishing line so that the end was about eight feet off the floor. I used a single ground stake and six 20ft radials.

Here are the results: SWR measured with MFJ 269 at end of 30ft of coax.Single earth stake and six 20ft radials

Wednesday, 14 October 2009

Slight change to the format this month. I was very pleased to meet Carl K9LA at the RSGB Convention last week. Carl is an HF propagation expert and a fellow member of the RSGB's Propagation Studies Committee.

I took the opportunity to talk with Carl about Solar Cycle 24. We also talked about the theory that galactic cosmic rays are affecting Top Band (160m) propagation during this solar minimum. You can listen to the podcast by clicking on the link above. Or you can search for G0KYA on iTunes.

Monday, 12 October 2009

I gave a talk at the RSGB's National Convention on WSPR, what it is and how it is being used. I was asked if I could make the PowerPoint presentation available so here it is. It is quite a big download though - about 12Mb. Just click on the title to download it.